The mitochondrial DNA (mtDNA) of multicellular animals is an excellent system to employ for studying evolutionary genetics at the molecular level. It is easily obtained in pure form. It is large enough to contain genes for 8-10 proteins, 2 ribosomal RNAs and 24 transfer RNAs, yet small enough to analyuze completely. It lacks intervening sequences, intergenic 'spacer' sequences and repretitive sequences, thus making its analysis relatively uncomplicated. Its gene content and relative gene order appear to be highly conserved, despite an extremely rapid rate of sequence evolution, and sequence rearrangements do not appear to occur over most of the genome. It is inherited maternally--clonally--and is thus free of the complications produced by biparental inheritance and recombination. Finally, changes in the mtDNA can be correlated with time, because the evolutionary history of the animals from which it comes is known from the fossil record. We propose to address two questions regarding the evolutionary molecular genetics of animal mtDNA: What kind of chages occur in mitochondrial DNA sequences, and in what proportions? How can the high rate of sequence evolution observed be tolerated in the genome of an intracellular organelle whose functions are so vital for the cell? To anser the first, we propose to obtain mtDNA from a series of seven primate species whose divergence times range from very recent to relatively ancient. The same three regions from each of the seven mtDNAs will be cloned and sequenced. The sequences will be compared, and the kinds and relative proportions of the changes determined. We also propose to examine two instances of sequence rearrangements in mtDNA, in order to gain insight into the mechanistic basis of this genetic change. To anser the second, we will analyze the sequence data with respect to what is known about the functions of the mitochondrial genes. The regions to be sequenced contain all types of genes found in mtDNA: genes for proteins, transfer RNAs, ribosomal RNAs and regulatory functions are represented. Methods include: ultracentrifugation, restriction analysis, cloning and sequencing, electron microscopyu, electrophoresis, DNA blotting, annealing and autoradiography.